Thin instrument cluster with anti-reflective coating

Abstract

An instrument display includes a light source that selectively emits light and a light guide that receives the light. One or more optical coating layers are disposed on the light guide. The light guide has a first index of refraction, and the optical coating layer or layers have a second index of refraction that is greater than the first index of refraction of the light guide. The optical coating layer or layers reduce glare from ambient light and increase the light transmitting performance of the light guide.

1. An instrument display comprising:
 a light source that selectively emits light, wherein the emitted light has a wavelength (λ); 
 a light guide receiving the light, wherein the light guide has a first index of refraction (n 1 ); and 
 at least one anti-reflective optical coating layer on the light guide, wherein the anti-reflective optical coating layer has a second index of refraction (n 2 ) that is greater than the first index of refraction of the light guide for preventing light from leaving the light guide in an undesired direction, and wherein the anti-reflective optical coating layer has a thickness (d) that is bused on the wavelength of the emitted light and the second index of refraction. 
 
   
   
     2. The display as recited in  claim 1 , wherein the light guide includes a first surface that faces in a first direction toward an instrument display lens and a second surface that faces in a second direction opposite of the first direction, wherein the at least one anti-reflective optical coating layer is on the first surface. 
   
   
     3. The display as recited in  claim 2 , wherein the at least one anti-reflective optical coating layer is also on the second surface. 
   
   
     4. The display as recited in  claim 3 , wherein the at least one anti-reflective optical coating layer comprises multiple anti-reflective optical coating layers, wherein each of the multiple anti-reflective optical coating layers is in direct contact with at least one other of the multiple anti-reflective optical coating layers. 
   
   
     5. The display as recited in  claim 4 , wherein the multiple anti-reflective optical coating layers are located one over another. 
   
   
     6. The display as recited in  claim 3 , wherein the at least one optical anti-reflective coating layer comprises at least five anti-reflective optical coating layers located one over another. 
   
   
     7. The display as recited in  claim 3 , wherein the light guide includes a graphic on the second surface. 
   
   
     8. The display as recited in  claim 1 , wherein the at least one anti-reflective optical coating layer is transparent or translucent. 
   
   
     9. A method comprising:
 depositing at least one anti-reflective optical coating layer on a light guide, wherein the light guide has a first index of refraction (n 1 ) and the at least one anti-reflective optical coating layer has a second index of refraction (n 2 ) that is greater than the first index of refraction of the light guide, and wherein the anti-reflective optical coating layer has a thickness (d) that is based on a wavelength of emitted light (λ) and the second index of refraction. 
 
   
   
     10. The method as recited in  claim 9 , including depositing the at least one anti-reflective optical coating layer on a first surface of the light guide that faces in a direction toward an instrument display lens. 
   
   
     11. The method as recited in  claim 10 , including depositing the at least one anti-reflective optical coating layer on a second, opposite surface of the light guide that faces in a direction away from the instrument display lens. 
   
   
     12. The method as recited in  claim 11 , including depositing a first layer of the at least one anti-reflective optical coating layer, and depositing a second layer of the at least one anti-reflective optical coating layer on the first layer. 
   
   
     13. The method as recited in  claim 11 , including printing a graphic on the second surface. 
   
   
     14. An instrument display comprising:
 a light source that selectively emits light; 
 a light guide receiving the light; 
 a first opaque optical coating layer directly on the light guide, wherein the first layer comprises a white paint; 
 a second opaque optical coating layer directly on the first layer, wherein the second layer comprises a black paint; and 
 a third opaque optical coating layer directly on the second layer, wherein the third layer comprises a paint having a different color than the black paint and the white paint. 
 
   
   
     15. The display as recited in  claim 14 , wherein the plurality of opaque optical coating layers includes an etched display mark that extends through two of the plurality of opaque optical coating layers. 
   
   
     16. The display as recited in  claim 14 , wherein the plurality of opaque optical coating layers are on two opposed surfaces of the light guide. 
   
   
     17. The display as recited in  claim 1 , wherein the light guide has an index of refraction between 1.5 and 1.6. 
   
   
     18. An instrument display comprising:
 a light source that selectively emits light; 
 a light guide receiving the light, wherein the light guide has a first index of refraction; and 
 at least one anti-reflective optical coating layer on the light guide, wherein the anti-reflective optical coating layer has a second index of refraction that is greater than the first index of refraction of the light guide for preventing light from leaving the light guide in an undesired direction, and wherein the light guide includes a first surface that faces in a first direction toward an instrument display lens and a second surface that faces in a second direction opposite of the first direction, wherein the at least one anti-reflective optical coating layer is on the first surface, and wherein a plurality of instrument display marks are on the second surface. 
 
   
   
     19. An instrument display comprising:
 a light source that selectively emits light; 
 a light guide receiving the light, wherein the light guide has a first index of refraction; and 
 at least one anti-reflective optical coating layer on the light guide, wherein the anti-reflective optical coating layer has a second index of refraction that is greater than the first index of refraction of the light guide for preventing light from leaving the light guide in an undesired direction, and wherein a thickness of the at least one anti-reflective optical coating layer varies for reflecting ambient light normal to the at least one anti-reflective optical coating layer. 
 
   
   
     20. An instrument display comprising:
 a light source that selectively emits light; 
 a light guide receiving the light, wherein the light guide has a first index of refraction; and 
 at least one anti-reflective optical coating layer on the light guide, wherein the anti-reflective optical coating layer has a second index of refraction that is greater than the first index of refraction of the light guide for preventing light from leaving the light guide in an undesired direction, and wherein the light guide includes a first surface that faces in a first direction toward an instrument display lens and a second surface that faces in a second direction opposite of the first direction, wherein the at least one anti-reflective optical coating layer is on the first surface, and where the first surface and the second surface intersect at a distal end of the light guide having a constant angle between the first surface and the second surface. 
 
   
   
     21. The display as recited in  claim 1 , wherein the thickness (d) is d=λ/(4n 2 ). 
   
   
     22. The display as recited in  claim 1 , wherein the second index of refraction (n 2 ) is n 2 =(n 1 +1)/2. 
   
   
     23. The method as recited in  claim 9 , wherein the thickness (d) is determined by the equation d=λ/(4n 2 ). 
   
   
     24. The method as recited in  claim 9 , wherein the second index of refraction (n 2 ) is determined by the equation n 2 =(n 1 +1)/2.